Although
we are getting better and better at it, forecasting the weather is still remarkably tricky. Far easier to predict the political
climate, especially when it comes to the issue of global warming. To wit: In December, negotiators from around the world will
meet in Kyoto to work out an international treaty to deal with what most (though not all) scientists
believe is a 0.5-degree-centigrade increase in temperatures over the past century, and the promise of more to come.

All major
participants, including the U.S. representatives, will argue that the only way to address global warming is to reduce significantly
levels of carbon dioxide and other greenhouse gases that are plausibly (though not definitively) linked to the rise in temperatures.
Although a group of small island nations will suggest a 20 percent reduction in greenhouse gases, members of the European
Union will most likely carry the day with a plan to cut emissions of carbon dioxide, methane, and nitrous oxide by at least
15 percent over the next decade.

The Clinton administration may object to those specific targets, but it will enthusiastically support
the consensus that the only way to counter global warming is by reducing emissions. Indeed, the president announced in August
that "we owe it to our children" to sign a treaty reducing consumption of greenhouse gases, a position echoed by Interior
Secretary Bruce Babbitt, who has called dissenters "un-American," and chief economic adviser Janet Yellen, who has called
cost-benefit analyses of cutting greenhouse gases "futile."

Such
thinking is perfectly in keeping with the universal environmentalist position, which is best understood as a starkly Puritan
ethic: "Abstain, sinner!" "The only way to slow climate change is to use less fuel," asserts Bill McKibben in The End of Nature,
a book that roundly condemns such luxuries as privately owned washing machines and oranges shipped to cold climates. And if
a 15 percent reduction in greenhouse gases seems extreme, consider that many ecologists champion far more costly conservation
measures as the only solution. Ross Gelbspan's The Heat Is On even urges a government takeover of the energy sector and a
massive propaganda campaign. In the wake of the Kyoto conference, expect to see calls for a Greenhouse Czar as global warming
is brought to broad, persistent public notice.

Such
hand wringing is as unimaginative as it is unequivocal. Instead of draconian cutbacks in greenhouse-gas emissions, there may
very well be fairly simple ways--even easy ones--to fix our dilemma. But the discussion of global warming never makes this
clear; it seems designed to preclude any hint that we might remedy the situation except through great sacrifice, discomfort,
and cost. Indeed, it seemingly assumes a direct relationship between the level of sacrifice, discomfort, and cost demanded
by any proposed solution and its scientific efficacy. Solutions based on suppressing fuel use will cost us dearly, in terms
of both dollars spent and standard of living. Economists differ over the price tag, with a rough analysis yielding an estimate
of about $250 billion a year to reduce carbon dioxide emissions alone by 15 percent worldwide. (This number is easily debatable
within a factor of two.) To this price we must add the cost of reducing other greenhouse gases, a cost felt not merely in
our pocketbooks but also in the goods, services, and innovations whose production would be halted or forgone.

But for
a number of reasons that I will discuss below, now is precisely the time to take seriously the concept of "geoengineering,"
of consciously altering atmospheric chemistry and conditions, of mitigating the effects of greenhouse gases rather than simply
calling for their reduction or outright prohibition. While such a notion may seem outlandish at first blush, it merely acknowledges
explicitly what everyone already understands: that human activity has an impact on the planet.

Forty
years ago, the noted atmospheric scientist Roger Revelle declared that "human beings are now carrying out a large scale geophysical
experiment" by pumping billions of tons of carbon dioxide into the air. The question before us should not simply be how best
to stop the experiment--and, by extension, the prosperity and progress allowed by cheap, abundant energy.

Rather,
the question should be how best to design that experiment, so that we maximize benefits and minimize costs. As the citizens
of the advanced nations become convinced that global warming is an immediate threat worthy of response, they will legitimately
ask for solutions that demand the least sacrifice.

Politics
and Parasols

A little-noticed
1992 NationalAcademy of Sciences panel report spoke directly to this issue. The report clarified the science behind global
warming and then ventured far from the ruling environmental orthodoxy: Could we accept that greenhouse gases will rise and
find ways to compensate for them? Instead of cutting gases, could we intervene to mitigate or offset the warming they may
cause?

Climate
modification is time-honored, though not clearly a winner. Cloud seeding in the United States during the 1940s and '50s met some success but ended in
a blizzard of lawsuits from those who claimed their local rainfall had been diverted by neighboring areas. (Though such assertions
had little scientific proof, courts felt otherwise.) During the Cold War, both sides studied a menu of climatic dirty tricks,
including schemes to kill the opponent's crops.

These
programs foundered on a fundamental fact: Before modifying a climate, one must first grasp it. At the level of understanding
available in the 1960s, only spectacular interventions would have left discernible signatures. Climate variability was so
little fathomed that weather prediction was pointless beyond roughly a week.

But in
progress little noticed by the public, systematic weather prediction has advanced more than tenfold in its assured time range.
By watching the sun, atmosphere, ocean, land, and clouds using satellites, advanced aircraft, ships, and a tight grid of land-based
observations, we have diminished the uncertainties about long-range weather. We are still just talking about the weather,
but the talk is of higher quality. Earlier this year, for instance, the National Oceanic and Atmospheric Agency predicted
a coming wet winter six months in advance, based on temperature measurements of tropical waters, presaging a new El Niño ocean
current. Whether that prediction is right or wrong--the coming months will decide--we are entering a new era in forecasting.
With the latest systems, backed by heavy computer modeling, we will shrink uncertainties, identify subtle feedback loops,
sniff out regional pollution patterns, discern the spread of deserts and the withering of forests.

Sensitive
global measures of disturbance will shed further light on polar and glacial contractions, ozone levels, volcanic dust, levels
of the oceans. There is even a technique available for cheaply gauging global reflectivity by measuring "earthshine"--the
faint glow of our reflected light, seen on the dark portion of a crescent moon. Using a small telescope and makeshift gear,
astronomers easily showed that we reflect 30 percent of incoming sunlight back into space--a number that our satellite system
got earlier, at a price tag of hundreds of millions of dollars. Such innovation will lessen the costs and confusions of global
understanding, a help we will need dearly if and when the greenhouse predicament worsens.

Geoengineering

Some
geoengineering systems appear possible to deploy now, and at reasonable cost. They could be turned on and off quickly if we
got unintended effects. It would be relatively easy to run small-scale experiments to answer questions about how our current
atmosphere behaves when one alters the kind of dust, or aerosols, in it. Nuanced knowledge is crucial; the biosphere is a
highly nonlinear system, one that has experienced climatic lurches before (glaciation, droughts) and can go into unstable
modes, too.

Indeed,
some critics argue that this simple fact precludes our tinkering with the "only Earth we have." Earth's climate might be chaotically
unstable, so that a state with only slightly different beginning conditions would evolve to end up markedly different: An
engineered early frost this year might mean an ice age the next. But we also know that Earth suffers natural injections of
dust and aerosols from volcanoes, driving weather changes. Experiments that affect the planet within this range of natural
variability could be allowed with little to no risk.

The simplest
way to remove carbon dioxide, the main greenhouse gas, is to grow plants--preferably trees, since they tie up more of the
gas in cellulose, meaning it will not return to the air within a season or two. Plants build themselves out of air and water,
taking only a tiny fraction of their mass from the soil. Forests, which cover about a third of the land, have shrunk by a
third in the last 10,000 years (though they have grown over the last half-century in the United States, mostly due to market forces).

Like
the ocean, land plants hold about three times as much carbon as the atmosphere. While oceans take many centuries to exchange
this mass with the air, flora take only a few years. As tropical societies clear the rain forest, the temperate nations have
actually been growing more trees, slightly offsetting this effect. In the United States, we have lost about a quarter of our forest cover since Columbus, and replanting occurs mostly in the South, where pine trees are a big cash crop for
the paper industry. But globally we destroy a forested acre every second. Just staying even with this loss demands a considerable
planting program.

Trees
soak up carbon fastest when young. Planting fast-growing species will give a big early effect, but what happens when they
mature? Eventually they either die and rot on the ground, returning nutrients to the soil, or we burn them. If this burning
replaces oil or coal burning, fine and good. Even felling all the trees still leaves some carbon stored longer as roots and
lumber. Buildings can hold lumber out of this cycle for a century or so.

About
half the U.S. carbon dioxide emissions could be captured if we grew
tree crops on economically marginal croplands and pasture. More forests could enhance biodiversity, wildlife, and water quality
(forests are natural filters); make for better recreation; and give us more natural wood products. Even better, one can do
the cheapest part first, with land nobody uses now. This would cost about $5 billion a year, and a feel-good campaign would
sell easily, with merchants able to proclaim their eco-virtue ("Buy a car, plant a grove of trees").

This
would work reasonably well in the short run. But trees take water, and one must be careful not to exhaust the soil, so this
is a solution with a clear horizon of about 40 years. Soaking up the world's present carbon dioxide increase solely through
trees would take up an Australia-sized land area--that is, a continent. Most such land is in private hands, so the job cannot
be done by government fiat. Still, a regional effort could make a perceptible dent in overall carbon dioxide levels.

The Geritol
Solution

The oceans
comprise the other great sink of greenhouse gases; some researchers estimate that they absorb 40 percent of fossil- fuel emissions.
In coastal waters rich in runoff, plankton can swarm densely, a million in a drop of water. They color the sea brown and green
where deltas form from big rivers, or cities dump their sewage. Tiny yet hugely important, plankton govern how well the sea
harvests the sun's bounty, and so are the foundation of the ocean's food chain. Far offshore, the sea returns to its plankton-starved
blue.

The oceans
are huge drivers in the environmental equations, because within them the plankton process vast stores of gases. Though cause
and effect are not quite clear, we do know that in ice ages, carbon dioxide levels dropped 30 percent.

Could
we do this today? Driving carbon dioxide down should lower temperatures, certainly. But how?

The answer
may lie not in the tropics but in the polar oceans, where huge reserves of key ingredients for plant growth--nitrates and
phosphates--drift unused. The problem is not weak sunlight or bitter cold, but lack of iron. Electrons move readily in its
presence, playing a leading role in trapping sunlight.

A radical
fix would be to seed these oceans with dissolved iron dust. This may have been the trigger that caused the big carbon dioxide
drop in the ice ages: The continents dried, so more dust blew into the oceans, carrying iron and stimulating plankton to absorb
carbon dioxide. Mother Nature can be subtle.

Such
an idea crosses the momentous boundary between quasi-natural mitigation such as tree planting and self-evidently artificial
means. Here is the nub of it, the conceptual chasm. With a boast that may cost his cause dearly, the inventor of the idea,
John Martin of the Moss Landing Marine Laboratories in California, said, "Give me half a tanker full of iron, and I'll give
you another ice age."

The captured
carbon gets tied up in a "standing crop" of plankton. These tiny creatures dwell within a few meters of the surface. To truly
bury the gas, they must somehow carry it into the vast bulk of the whole ocean. Some biologists believe that from the plankton
the carbon dioxide should slowly dissolve into the lower waters, though we are uncertain of this. Perhaps the carbon dioxide
eventually is deposited on the seabed. This last process no one has checked. Somehow, though, a good dealof carbon does end up in the deep ocean sinks.

First
proposed by Martin in 1988, the "Geritol solution" of adding iron to the ocean had a rocky history. Many derided it automatically
as foolish, arrogant, and politically risky. But in 1996 the idea finally got tested by the U.S. government, and it performed well. Near the Galapagos Islands lies
a fairly biologically barren area. Over 28 square miles of blue sea, scientists poured 990 pounds of iron during a week of
testing. Immediately the waters bloomed with tiny phytoplankton, which finally covered 200 square miles, suddenly green. Plankton
production peaked nine days after the experiment started. One thousand pounds of iron dust stimulated over 2,000 times its
own weight in plant growth, far greater than the performance of any fertilizer on land. The plankton soaked up carbon dioxide,
reducing its concentration in nearby sea water by 15 percent. It quickly made up this deficiency by drawing carbon dioxide
from the air.

Projections
show that since this process would affect only about 16 percent of the ocean area, a full-bore campaign to dump megatons of
iron into the polar oceans probably would suck somewhere between 6 percent and 21 percent of the carbon dioxide from the atmosphere,
with most recent estimates settling around 10 percent. Such scary, big-time tinkering is the extreme; the method would have
to be tested at far lower levels. Still, this mitigation could dent the greenhouse problem, though not solve it entirely.

Even
such partial solutions attract firm opponents. Geoengineering carries the strong scent of hubris. What is best described as
eco-virtue reared its head immediately after the 1988 proposal, even before any experiments took place. Following the Puritan
model that any deviation from abstinence is itself a further indulgence, many scientists and ecologists saw in Martin's plan
an incentive for polluters. "A lot of us have an automatic horror at the thought," commented atmospheric authority Ralph Cicerone
of the University of California at Irvine.

Other
specialists retaliated. Russell Seitz of Harvard said the Galapagos experimenters were afraid to seem politically incorrect.
"If this approach proves to be environmentally benign," Seitz said, "it would appear to be highly economic relative to a Luddite
program of declaring war against fire globally."

Large
uncertainties remain: How would the iron affect the deeper ecosystems, of which we know little? Will the carbon truly end
up on the seabed? Can the polar oceans carry the absorbed carbon away fast enough to not block the process? Would the added
plankton stimulate fish and whale numbers in the great Antarctic Ocean? Or would some side effect damage the entire food pyramid? Even if the idea worked, who should run such a program?
Additionally, there is some evidence that little of the newly fixed carbon in the Galapagos experiment actually sank.

It
seems to have come back into chemical equilibrium with the air. Controversy surrounds this essential point; clearly, here
is where more research could tell us much.

This
much seems certain (and should allay many fears): If we decide to stop the Geritol solution because of unforeseen side effects,
control is easy. The standing crop will die off within a week, providing a quick correction.

Costs,
too, are easy to figure. There is nothing very high-tech about dumping iron. Martin estimated that the job would take about
half a million tons per year. Depending on what sort of iron proves best at prodding plankton, and implementation methods,
the iron costs range between $10 million and $1 billion a year. Throwing in 15 ships steaming across the polar oceans all
year long, dumping iron dust in lanes, brings the total to around $10 billion. This would soak up about a third of our global
fossil-fuel-generated carbon dioxide emissions each year.

Reflecting
on Reflectivity

Not all
mitigation efforts need take place on land or sea. In fact, the most intuitive approach may be simply to reflect more sunlight
back into space, before it can be emitted in heat radiation and then absorbed by carbon dioxide. People understand the basic
concept readily enough: Black T-shirts are warmer in summer than white ones. We already know that simply painting buildings
white makes them cooler. We could compensate for the effect of all greenhouse gas emissions since the Industrial Revolution
by reflecting less than 1 percent more of the sunlight.

A mere
0.5 percent change in Earth's net reflectivity, or albedo, would solve the greenhouse problem completely. The big problem
is the oceans, which comprise about 70 percent of our surface area and absorb more light because they are darker than land.

When
it comes to increasing albedo, it would be wise to begin the discussion by introducing positive measures that can be easily
understood and are close at hand. Reflecting sunlight is not a deep technical idea, after all. Simply adding sand or glass
to ordinary asphalt ("glassphalt") doubles its albedo. This is one mitigation measure everyone could see--a clean, passive
way to Do Something.

A 1997
UCLA study showed that Los
Angeles is 5 degrees
Fahrenheit warmer than the surrounding areas, mostly due to dark roofs and asphalt. Cars and power plants contribute, but
only a bit; at high noon, the sun delivers to each square mile the power equivalent of a billion-watt electrical plant.

This
urban "heat island" effect is common. But white roofs, concrete-colored pavements, and about $10 billion in new shade trees
could cool the city below the countryside, cutting air conditioning costs by 18 percent. Cooler roads lessen tire erosion,
too. About 1 percent of the United States is covered by human constructions, mostly paving, suggesting that we may already control enough of the land to get
at the job.

From
such homegrown solutions, we could make the leap to space. The most environmentally benign proposal for increasing the planet's
albedo is very high-tech (and expensive): a massive orbiting white screen, about 2,000 kilometers on a side. Even if such
parasols were broken into small pieces, putting them up would cost about $120 billion, a bit steep. We would also have to
pay a lot to take them down if they caused some undesirable side effects. (One is certain: a night sky permanently light-polluted,
irritating astronomers and moonstruck lovers.)

Using
more-innocuous dust to reflect sunlight does not work; it drifts away, driven off by the sun's light pressure. But the upper
atmosphere is still a good place to intervene, because much sunlight gets absorbed in the atmosphere on its way to us. Also,
measures far above our heads trouble us less.

Other
sorts of reflectors at high altitudes are promising. Spreading dust in the stratosphere appears workable because at those
heights tiny particles stay aloft for several years. This is why volcanoes spewing dust affect weather strongly. The tiny
motes that redden our sundowns reflect more sunlight than they trap infrared.

Even
better than dust are microscopic droplets of sulfuric acid, which reflects light more effectively. Sulfate aerosols can also
raise the number of droplets that make clouds condense, further increasing overall reflectivity. This could then be a local
cooling, easier to monitor than carbon dioxide's global warming. We could perform such small, controllable experiments now.
The amount of droplets or dust needed is a hundredth of the amount already blown into the atmosphere by natural processes,
so we would not be venturing big dislocations. And we would get some spectacular sunsets in the bargain.

As usual,
there are human-centered concerns. The Environmental Protection Agency hammers away at particulate levels, blaming them for
lung disorders. Luckily, high- altitude dust would come down mostly in raindrops, not making us cough. The cheapest way of
delivering dust to the stratosphere is to shoot it up, not fly it. Big naval guns fired straight up can put a one-ton shell
20 kilometers high, where it would explode and spread the dust. This costs only a hundredth as much as the space-parasol idea.
But booming naval guns that rattle windows for miles around are likely to provoke more than a few Not in My Backyard reactions.

Fortunately,
there is a ready alternative to dust in any form: jet fuel. Changing the fuel mixture in a jet engine to burn rich can leave
a ribbon of fog behind for up to three months, though as it spreads it becomes invisible to the eye. These motes would also
come down mostly in rain, not troubling the brow of the EPA. Fuel costs about 15 percent of airlines' cash operating expenses,
and running rich increases costs by only a few percent. For about $10 million, this method would offset the 1990 U.S. greenhouse emissions. Adding this to the cost of an airline ticket would boost prices
perhaps 1 percent. An added asset is that quietly running rich on airline fuel will attract little notice, doesn't even change
sunsets, and is hard to muster a media-saturated demonstration against.

But there
are, as always, side effects. Dust or sulfuric acid would heat the stratosphere, too, with unknown impact. Some scientists
suspect the ozone layer could be affected. If a widespread experiment showed this, we could turn off the effect within roughly
a year as the dust settled down and got rained out. (Smaller experiments should show this first, of course.)

These
ideas envision doing what natural clouds do already as the major players in the total albedo picture. A 4 percent increase
in stratocumulus over the oceans would offset global carbon dioxide emission. Land reflects sunlight much better than the
wine-dark seas, so putting clouds far out from land, and preferably in the tropics, gets the greatest leverage.

Clouds
condense around microscopic nuclei, often the kind of sulfuric acid droplets the geoengineers want to spread in the stratosphere.
The oceans make such droplets as sea algae decays, and the natural production rate sets the limit on how many clouds form
over the seas. Clouds cover about 31 percent of our globe already, so a 4 percent increase is not going to noticeably ruin
anybody's day.

Tinkering
with such a mammoth natural process is daunting, but in fact about 400 medium-sized coal-fired power plants give off enough
sulfur in a year to do the job for the whole Earth. (This in itself suggests just how much we are already perturbing the planet.)
There are problems with using coal: Arguing that more air pollution is good for Mother Earth sounds intuitively wrong. Coal
plants sit on land, and the clouds would be most effective over the oceans. A savvy international strategy leaps to mind:
Subsidize electricity-dependent industry on isolated Pacific islands, and ship them the messiest, sulfur-rich coal. The plants'
plumes would stretch far downwind, and the manufactured goods could revitalize the tropical ocean states, paying them for
being global good neighbors. The wealthy states would then get their mitigation carried out far from home and far from vexatious
neighborhood committees, using labor purchased at low rates. And nobody has to take the plants; prices will mediate the demand.

A more
boring approach, worked out by the NationalAcademy of Sciences panel, envisions a fleet of coal-burning ships which heap sulfur directly
into their furnaces. (Maybe some collaboration would work here. Freighters burning sulfur could also spread iron dust, combining
the approaches, with some economies.) The ships spew great ribbons of sulfur vapor far out at sea, where nobody can complain,
and cloud corridors form obediently behind. It would be best to use these sulfur clouds to augment the edges of existing overcast
regions, swelling them and increasing the lifetime of natural clouds. The continuously burning sulfur freighters would follow
weather patterns, guided by weather satellite data.

At first
these could operate as regional experiments, to work out a good model of how the ocean's cloud system responds. This low-tech
method would cost about $2 billion per year, including amortizing the ships.

The biggest
political risk here lies with shifts in the weather. The entire campaign would increase the sulfur droplet content in our
air by about 25 percent. Probably this would cause no significant trouble, with most of the sulfur raining out into the oceans,
which have enormous buffering capacity. Keeping the freighters a week's sailing distance from land would probably save us
from scare headlines about sudden acid rains on farmers' heads, since about 30 percent of the sulfur should rain out each
day.

Albedo
Chic

The NAS
panel found that "one of the surprises of this analysis is the relatively low cost" of implementing some significant geoengineering.
It might take only a few billion dollars to mitigate the U.S. emission of carbon dioxide. Compared with stopping people in China from burning coal, this is nothing.

We should
not take the 1992 panel report, thick with footnotes and layers of qualifiers, to be a road map to a blissful future. The
NAS estimates are simple, linear, and made with poorly known parameters. They also ignore many secondary effects. For example,
forests promote clouds above them, since the water vapor they exhale condenses quickly. Those lovely cumulus puffs reflect
sunlight. So growing trees to sop up carbon dioxide also increases albedo, a positive feedback bonus. But is that the end
of the chain? No, because water vapor itself is a greenhouse gas. Thick clouds absorb infrared as well. If forests respire
a lot, they can partially trap their own heat. Understanding this, and calculating it in detail, will take a generation of
research.

But perhaps
the greatest unknown is social: How will the politically aware public react--those who vote, anyway? If geoengineers are painted
early and often as Dr. Strangeloves of the air, they will fail. Properly portrayed as allies of science--and true environmentalism--they
could become heroes. Not letting the radical greens set the terms of discussion will matter crucially.

A major
factor here will be whether mitigation looks like yet another top-down contrivance, another set of orders from the elite.
Draconian policing of fuel burning will certainly look that way, a frowning Aunt Bessie elbowing into daily details, calculating
your costs of commuting to work and setting your thermostat level. In contrast, mitigation does not have to push a new camel's
nose into our tents. Technical solutions can play out far from people's lives, on the sea or high in the air.

Better,
widespread acceptance of mitigation strategies could lead to an albedo chic--ostentatious flaunting of white roofs, the Mediterranean
look, silvered cars, the return of the ice-cream suit in fashion circles. White could be appropriate after Labor Day again.

More
seriously, every little bit would indeed help. This is crucial: Mitigation wears the white hat. It asks simple, clear measures
of everyone, before going to larger-scale interventions. Grassroots involvement should be integral from the very beginning.
Local efforts should go apace with those at the nation-state level, especially since mitigation intertwines deeply with diplomacy.
Here appearances are even more critical, given the levels of animosity between the big burners (especially the United States) and the tropical world.

Plausible
solutions should stay within the NAS panel's sober guidelines. Learning more is the crucial first step, of course. This is
not just the usual academic call for more funded research; nobody wants to try global experiments on a wing and a prayer.

Beyond
more studies and reports, we must soon begin thinking of controlled experiments. Climate scientists so far have studied passively,
much like astronomers. They have a bias toward this mode, especially since the discernible changes we have made in our climate
generally have been pernicious. Such mental sets ebb slowly. The reek of hubris also restrains many. But a time for many limited
experiments like the iron-dumping one will come. This will be the second great step as we ponder whether to become geoengineers.
Constraints must be severe to ensure clear results.

Most
important, perturbations in climate must be local and reversible--and not merely to quiet environmentalist fears. Only controlled
experiments, well designed and well analyzed, will be convincing to all sides in this debate. Indeed, the green plume near
the Galapagos Islands showed this. Its larger features were best studied by
satellite, which picked up the green splotch strongly against the dark blue sea. But the crucial issue of whether the carbon
stayed tied up in ocean waters was poorly addressed. Satellites were of no help. Slightly better funding and more scientists
in dispersed, small craft could have told us a lot more.

Careful
climate modeling must closely parallel every experiment. Few doubt that our climate stands in a class by itself in terms of
complexity. Though much is made of how wondrous our minds are, perhaps the most complex entity known is our biosphere, in
which we are mere mayflies. Absent a remotely useful theory of complexity in systems, we must proceed cautiously.

While
computer studies are notorious for revealing mostly what was sought, confirming the prejudices of their programmers, methods
are improving quickly. They can explore the many side avenues of small-scale geoengineering experiments. Invoking computer
models as crucial watchdogs in every experiment will calm fears, at least among those who read beyond the headlines.

Who pays,
in the end? Political pressure may well compel nations to comply with some target goals. A crucial factor will be what ratio
to use in assessing a nation's (or region's) rectitude: net fossil-fuel consumption divided by what? Population? This favors
the poor and populous nations. Economic value created with the fuels? The United States would fare reasonably well. Some weighted mean between the two?

To avoid
descending into pure power politics and making policy sausage in public, a World Warming Authority could copy our fledgling
pollution-voucher methods, bringing some market forces into play. But instead of simply trading the right to burn more--a
negative unit--one could use a positive Mitigation Unit as well. Industries amassing them by, say, paying for rich-burning
jet fuel could then burn more oil themselves. A market-driven dynamic equilibrium could then minimize costs for a given anti-warming
target.

Such
approaches might drive the emergence of suites of methods, which regions could choose among to their best advantage. Deserts
reflect light well (though their roads are usually dark), so added cloud cover is less effective there overall; the whitewashing
of cities could be measured by their average decrease in the heat-island effect; lands with high rainfall may favor forestation.
Any such policy calculus should hover over theintricacies of markets, which
will move faster and with more ingenuity than any committee. Rigid mandates will inevitably fail.

Still,
going from the local to the global is fraught with uncertainty--and sure to inspire much anxiety. We will always be ambivalent
stewards of the Earth. And greenhouse gas emissions certainly will not be our last problem, either. We are doing many things
to our environment, with our numbers expected to reach 10 billion by 2050. What new threats will emerge? Catastrophes may
come at a quickening pace, springing from the many synergistic effects that we must trace through the geophysical labyrinth.

As we
begin correcting for our inadvertent insults to Mother Earth, we should realize that it's forever. Once we become caretakers,
we cannot stop. The large tasks confronting humanity, especially the uplifting of the majority to some semblance of prosperity,
must be carried forward in the shadow of our stewardship.

And yet,
even among the able nations, those who have the foresight to grasp solutions, an odd reluctance pervades the policy classes.
As the atmospheric physicist Ralph Cicerone has noted, "Many who envision environmental problems foresee doom and have little
faith in technology, and therefore propose strong limits on industrialization, while most optimists refuse to believe that
there is an environmental problem at all."

Having
sinned against Mother Nature inadvertently, many are keenly reluctant to intervene knowingly. Sherwood Rowland, a chemist
at the University of California at Irvine who predicted, with Mario Molina, the depletion of the ozone layer, declared, "I
am unalterably opposed to global mitigation." This added considerable weight to the abstention cause. At root, such people
see mankind as the problem; only by behaving humbly, living lightly upon our Earth, can we atone. Here most scientists and
theologians agree, at least for now.

The next
century will see a protracted battle between the prophets who would intervene and the moralists who see all grand-scale human
measures as tainted. Even now, many argue that even to speak of geoengineering encourages the unwashed to more excess, since
the masses will think that once again science has a remedy at hand.

Last year in April, at a sf convention here in Canberra, I watched a presentation on global warming by GregoryBenford, supposedly telling us about a global warming summit that he had recently participated in. Anticipating the nature of his audience, he first showed us the summit's deliberately conservative final
numbers on temperature rise, carbon dioxide levels etc for the next 26 years, then quickly demolished some popular but flawed
solutions with clear logic and straightforward calculation.

As a result of attending Greg's little overhead-projected show, I now believe
that the cheapest, most effective and most practical answer to global warming is to think like a supervillain and block out
the sun's rays using a giant rotating Space Lens suspended directly in front of the Sun! Muahahaha!

Let
me tell you why:

Gregory
Benford is a professor of plasma physics and astrophysics at the University of California, and received his PhD in 1967. He's been an adviser for NASA, the Department of Energy and the White
House Council on Space Policy, and attended the first NSF global warming summit back in 1992. He's also a writer, and has
bashed out some of the best hard sci-fi novels of the modern age, including Timescape, Cosm, and the Galactic Center Saga
which spanned six books from In The Ocean Of Night to Sailing Bright Eternity.

This experience of painting mind-expanding mental images with strict scientific
accuracy allowed him to give a very complete picture of the challenges of global warming, free of the usual distortions, half-remembered
statistics and lies motivated by personal gain.

Using the "best case" global warming numbers agreed on by the summit to destroy
one solution popular among the ignorant, he showed that for nuclear power to make enough of a difference to stop global
warming by 2030, the world would have to replace the electrical output of one large coal-fired power station with an equivalent
nuclear power station, EVERY DAY for the next 25 years. Every damn day. 365 per year. I would
not have believed the figures if I hadn't seen every step of his working-out in that meeting.

Stopping global warming by 2030 is vital because it is a tipping-point where
the rising temperatures begin to trigger the release of carbon dioxide and methane from natural sources, which raise temperatures,
which release more carbon etc; in other words, after the expected temperature rise by 2030, we will experience a runaway greenhouse
effect resulting in huge increases of eight degrees Celsius or more by 2100.

The effect of an eight degree rise in global temperatures would be catastrophic.
One effect would be rising seas flooding the land upon which around half the world's population currently lives. Another would
be the destruction of biodiversity on a scale dwarfing even our current extinction rate, as entire populations desperately
flee to remote areas, rising seas drown whole ecosystems, and habitats disappear due to the climate shift.

In any case, it is clearly impossible for us to stop global warming solely
by replacing our current and future power generation with nuclear power. Quite apart from the expense of building a new nuclear
power station every day for 25 years, there is not enough nuclear fuel on the planet to cope with the demand. We must think
of other ways, such as solar, wind, geothermal or tidal power, architectural albedo modification (Painting roofs and roads
white, since white will reflect sunlight more effectively and increase Earth's reflectivity), geoengineering (from filling
the stratosphere with silver foil to burying carbon dioxide in the ocean) and lifestyle changes.

However, if we're realistic, the governments of the world will never be up
to the huge plethora of detail this multifaceted solution would entail. I personally think that Gregory Benford's plan, which
he presented to the summit and showed us in the talk, is the best (cheapest, most practical and most effective) option we've
currently got available. It is also the most fun, though an atmosphere full of floating silver foil might be a close second
until planes start flying through air-drifts of foil and their engines explode.

Dr Benford, while doing most of the work himself, has exploited his friends
at NASA to confirm that the engineering is viable, and the results were astounding: The whole project could be achieved with
today's technology at a cost of $10 billion US dollars up-front, and another ten for maintenance over the decades of designed
lifespan.

That's a lot of money, but it's still about two-fifths of the initial appropriation
from Congress for the Iraq war. Benford proposes an international collaboration between wealthy nations to spread the load,
and I would also suggest commercial sponsors. This would make the project almost indecently viable, considering the return
each nation would get from being able to ignore Kyoto and its successors for as long as they feel like.

Gregory Benford's idea is to build a concave Fresnel Lens 1000 kilometres across
but only a few millimetres thick at the L1 stable orbital point between us and the Sun, to slightly diffuse its light and
cool us down enough to balance the warming effect of carbon dioxide, methane etc.

A few explanations are in order for that sentence:

The L1 (Lagrange 1) point is a point in space on a direct
line between the Earth and the sun, 1.5 million kilometres away from our little blue dot. At that point, the gravity of the
Earth is balanced with that of the Sun in such a way that anything placed there will, if gently nudged back into place every
25 days or so, orbit the Sun once every year. This means that it will remain directly between Earth and Sun with almost no
fuel expenditure. Currently there's a solar observatory satellite called SOHO there. It may have to move.

A Fresnel lens is simply a magnifying (convex, outward curving)
or diffusing (concave, inward curving) glass, with all the useless inside glass taken out and the lens concentrically cut
into thousands of ringlike sections. If you've seen a lighthouse's light up close, or one of those flat sheets of plastic
that nevertheless magnifies things, you've seen a convex Fresnel lens.

Dr Benford's circular,
millimetres-thin Lens would be made from an advanced plastic, and would need to be adjustable to fine-tune the amount of light
that it prevented from reaching the Earth. Benford proposes spinning the 1000-kilometre structure fast enough to stiffen and
maintain its shape. The Lens would need thrusters around its rim to keep from drifting away, and these may also assist the
focussing and spinup stages.

The reduction in incoming sunlight would be 0.5 to 1%, enough to neatly stop
global warming and keep temperatures stable. It would give us time to stabilise our emissions, then start the long process
of filtering greenhouse gases back out of the atmosphere and storing them somewhere. The Lens can of course be adjusted, so
as greenhouse gas levels dropped the diffusion effect would be reduced as well, until we reached a point where the Lens was
no longer required and could be safely dismantled, or more playfully used to frighten the hell out of everyone in a medium-sized
nation with an appropriate orbital insertion to enter the Earth's atmosphere flat-on.

The downside of this approach is that the other effects of the increased
carbon dioxide would have to be addressed, such as increased plant growth (great if you like weeds) and less of an incentive
not to pollute the air with fossil fuels. Coal might seem like an even better option to fast-growing developing countries
like China, Brazil and Nigeria, meaning sooty, gritty misery for anyone living nearby, unless stringent pollution standards are
internationally enforced somehow.

More info on the L1 point and Gregory Benford can be reached on Google, while
the continuing progress of the 1-kilometre high, no-emission, oxygen-producing, 200-megawatt Australian solar tower which
will be built by 2009 at Buronga, 25 ks east of Mildura in New South Wales, can be found here. The project has just recently purchased the land they plan to build upon, and has
so far defied the usual predictions of failure that accompany any new way of doing things. Here's hoping that the SolarTower is successful, just so some madman decides to build a 2-kilometre high one to show up those damn
Aussies.